Method and apparatus for executing conditional handover in wireless communication network

ABSTRACT

A method for executing conditional handover by a UE in a wireless communication network is provided. The method may include receiving an RRC reconfiguration message from a source cell of the wireless communication network. The RRC reconfiguration message may include a handover configuration and determining whether a CHO configuration may be provided in the handover configuration. Further, the method may include performing one of: continuing an RLM timer and an RLM procedure on the source cell, in response to determining that the CHO configuration is provided in the handover configuration; and stopping the RLM timer and suspending the radio link monitoring procedure on the source cell, in response to determining that the CHO configuration is not provided in the handover configuration. The method may then include executing the CHO from the source cell to a candidate target cell in the wireless communication network based on the CHO configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/835,014,filed Mar. 30, 2020, now U.S. Pat. No. 11,317,335, which is based on andclaims priority under 35 U.S.C. § 119 of an Indian patent applicationnumber 201941012734, filed on Mar. 29, 2019, in the Indian PatentOffice, and of an Indian patent application number 201941012734, filedon Mar. 25, 2020, in the Indian Patent Office, the disclosures of whichare herein incorporated by reference in their entirety.

BACKGROUND 1. Field

The present disclosure relates to in wireless communication, and moreparticularly to a method and a user equipment (UE) for executingconditional handover in a wireless communication network.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4th generation (4G) communication systems, efforts havebeen made to develop an improved 5th generation (5G) or pre-5Gcommunication system. The 5G or pre-5G communication system is alsocalled a ‘beyond 4G network’ or a ‘post long term evolution (LTE)system’. The 5G communication system is considered to be implemented inhigher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplishhigher data rates. To decrease propagation loss of the radio waves andincrease the transmission distance, beamforming, massive multiple-inputmultiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna,analog beamforming, and large scale antenna techniques are discussedwith respect to 5G communication systems. In addition, in 5Gcommunication systems, development for system network improvement isunder way based on advanced small cells, cloud radio access networks(RANs), ultra-dense networks, device-to-device (D2D) communication,wireless backhaul, moving network, cooperative communication,coordinated multi-points (CoMP), reception-end interference cancellationand the like. In the 5G system, hybrid frequency shift keying (FSK) andFeher's quadrature amplitude modulation (FQAM) and sliding windowsuperposition coding (SWSC) as an advanced coding modulation (ACM), andfilter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA),and sparse code multiple access (SCMA) as an advanced access technologyhave been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofeverything (IoE), which is a combination of the IoT technology and thebig data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “security technology” have been demanded forIoT implementation, a sensor network, a machine-to-machine (M2M)communication, machine type communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing information technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies such asa sensor network, MTC, and M2M communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RAN as theabove-described big data processing technology may also be considered tobe as an example of convergence between the 5G technology and the IoTtechnology.

As described above, various services can be provided according to thedevelopment of a wireless communication system, and thus a method foreasily providing such services is required.

SUMMARY

Accordingly the embodiments herein disclose a method for executingconditional handover by UE in a wireless communication network. Themethod may include receiving an RRC reconfiguration message from asource cell of the wireless communication network. The RRCreconfiguration message may include a handover configuration. The methodmay further include determining whether a CHO configuration is providedin the handover configuration. The CHO configuration may include aplurality of conditions for performing the CHO and a plurality of targetcell configurations. Further, the method may include performing one of:continuing an RLM timer and an RLM procedure on the source cell, inresponse to determining that the CHO configuration is provided in thehandover configuration; and stopping the RLM timer and suspending theradio link monitoring procedure on the source cell, in response todetermining that the CHO configuration is not provided in the handoverconfiguration. The method may then include executing the CHO from thesource cell to a candidate target cell of the plurality of target cellsin the wireless communication network based on the CHO configuration.

In an embodiment, executing by the UE, the CHO from the source cell tothe candidate target cell of the plurality of target cells in thewireless communication network based on the CHO configuration mayinclude determining that the condition for executing the CHO from thesource cell to the candidate target cell is fulfilled; suspending theRLM timer and the radio link monitoring procedure on the source cell;and executing the conditional handover from the source cell to thecandidate target cell in the wireless communication network based on thecandidate target cell configuration of the plurality of target cellconfiguration.

In an embodiment, the CHO configuration may include a condition forexecuting the CHO for the candidate target cell and a candidate targetcell configuration.

In an embodiment, the plurality of target cell configurations may becarried in the RRC reconfiguration message as an OCTET string.

In an embodiment, the CHO configuration may be a delta configuration toa current source cell configuration.

In an embodiment, the plurality of target cell configurations in the CHOconfiguration cannot be altered by the source cell.

In an embodiment, the condition for performing the CHO may be determinedand appended by the source cell to the CHO configuration.

In an embodiment, the RLM Timer may be a T310 timer.

Accordingly the embodiments herein disclose user equipment (UE) forexecuting conditional handover in a wireless communication network. TheUE may include a transceiver, a memory, and at least one processor. Theat least one processor may be configured to control the transceiver toreceive an RRC reconfiguration message from a source cell of thewireless communication network, where the UE is in an RRC connectedstate and where the RRC reconfiguration message comprises a handoverconfiguration. The at least one processor may be further configured todetermine whether a conditional handover (CHO) configuration is providedin the handover configuration, where the CHO configuration may include aplurality of conditions for performing the CHO and a plurality of targetcell configurations. Further, the at least one processor may be alsoconfigured to perform one of: continue a radio link monitoring (RLM)timer and a radio link monitoring procedure on the source cell, inresponse to determining that the CHO configuration is provided in thehandover configuration; and stop the RLM timer and suspending the radiolink monitoring procedure on the source cell, in response to determiningthat the CHO configuration is not provided in the handoverconfiguration. Further, the at least one processor may be alsoconfigured to execute the CHO from the source cell to a candidate targetcell of the plurality of target cells in the wireless communicationnetwork based on the CHO configuration.

Accordingly the embodiments herein disclose a method for triggering anRRC state transition indication by UE in a wireless communicationnetwork. The method includes receiving, by the UE, a radio resourcecontrol (RRC) Reconfiguration message from the wireless communicationnetwork, where the RRC Reconfiguration message comprises a configurationsetting. Further, the method includes enabling, by the UE, a capabilityto trigger an RRC state transition indication to the wirelesscommunication network based on the configuration setting anddetermining, by the UE, a condition to trigger the RRC state transitionindication to the wireless communication network is satisfied. Further,the method includes triggering, by the UE, the RRC state transitionindication by sending a UE assistance information message to thewireless communication network.

Accordingly the embodiments herein disclose user equipment (UE) fortriggering an RRC state transition indication in a wirelesscommunication network. The UE includes a communicator, a memory, and aprocessor. The communicator is configured to receive a radio resourcecontrol (RRC) Reconfiguration message from the wireless communicationnetwork, where the UE is in an RRC_CONNECTED state and where the RRCReconfiguration message comprises a configuration setting. The processoris configured to enable a capability to trigger an RRC state transitionindication to the wireless communication network based on theconfiguration setting. Further, the processor is also configured todetermine a condition to trigger the RRC state transition indication tothe wireless communication network is satisfied; and trigger the RRCstate transition indication by sending a UE assistance informationmessage to the wireless communication network.

These and other aspects of the embodiments herein will be betterappreciated and understood when considered in conjunction with thefollowing description and the accompanying drawings. It should beunderstood, however, that the following descriptions, while indicatingpreferred embodiments and numerous specific details thereof, are givenby way of illustration and not of limitation. Many changes andmodifications may be made within the scope of the embodiments hereinwithout departing from the spirit thereof, and the embodiments hereininclude all such modifications.

The principal object of the embodiments herein is to provide a methodand a UE for executing conditional handover in a wireless communicationnetwork.

Another object of the embodiments herein is to receive an RRCreconfiguration message comprising a handover configuration from asource cell of the wireless communication network.

Another object of the embodiments herein is to determine that a CHOconfiguration which includes a plurality of conditions for performingthe CHO and a plurality of target cell configurations is provided in thehandover configuration.

Another object of the embodiments herein is to continue an RLM timer anda radio link monitoring procedure on the source cell, in response todetermining that the CHO configuration is provided in the handoverconfiguration; and stop the RLM timer and suspend the radio linkmonitoring procedure on the source cell, in response to determining thatthe CHO configuration is not provided in the handover configuration.

Another object of the embodiments herein is to execute the CHO from thesource cell to a candidate target cell of the plurality of target cellsin the wireless communication network based on the CHO configuration.

Another object of the embodiments herein is to suspend the RLM timer andthe radio link monitoring procedure on the source cell when thecondition for executing the CHO from the source cell to the candidatetarget cell is fulfilled.

Another object of the embodiments herein is to enable the UE to send anRRC state transition indication to the wireless communication networkbased on a configuration setting received in the RRC Reconfigurationmessage.

Another object of the embodiments herein is to determine that at leastone condition to trigger the RRC state transition indication to thewireless communication network is satisfied.

Another object of the embodiments herein is to trigger the RRC statetransition indication by sending a UE assistance information message tothe wireless communication network.

Another object of the embodiments herein is to append a preferred RRCstate of the UE in the UE assistance information message.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same. It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for certain words and phrases are provided throughout thispatent document, those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1A illustrates a system for executing conditional handover in awireless communication network, according to the embodiments asdisclosed herein;

FIG. 1B illustrates a block diagram of a user equipment (UE) forexecuting the conditional handover in the wireless communicationnetwork, according to the embodiments as disclosed herein;

FIG. 2A illustrates a flow chart of a method for executing theconditional handover by the UE in the wireless communication network,according to the embodiments as disclosed herein;

FIG. 2B illustrates a flow chart of a method for triggering an RRC statetransition indication by the UE in the wireless communication network,according to the embodiments as disclosed herein;

FIG. 3A illustrates a signaling diagram of a suspension of a radio linkmonitoring (RLM) timer immediately on receiving a handover command (HO),according to the embodiments as disclosed herein;

FIG. 3B illustrates a signaling diagram of a continuation of the RLMtimer on a source cell till HO execution based on a conditional handoverconfiguration provided in the HO command, according to the embodimentsas disclosed herein;

FIG. 4 illustrates a flow chart of an RLM monitoring during the HOexecution, according to the embodiments as disclosed herein;

FIG. 5A illustrates a signaling diagram of pro-active neighbor cellpreparation for re-establishment, according to the embodiments asdisclosed herein;

FIG. 5B illustrates a signaling diagram of target cell preparation forthe HO execution, according to the embodiments as disclosed herein;

FIG. 6 illustrates a flow chart of cell selection prioritization (order)when attempting re-establishment, according to the embodiments asdisclosed herein;

FIG. 7A illustrates a signaling diagram of a method of performing a UEcontrolled RRC_CONNECTED to RRC_INACTIVE state transition as on aconfigured threshold, according to the embodiments as disclosed herein;

FIG. 7B illustrates a signaling diagram of a method of performing the UEcontrolled RRC_CONNECTED to RRC_INACTIVE state transition as on aconfigured timer, according to the embodiments as disclosed herein;

FIG. 7C illustrates a signaling diagram of a method of performing the UEautonomous RRC_CONNECTED to RRC_IDLE state transition as on a configuredtimer, according to the embodiments as disclosed herein;

FIG. 8 illustrates a gNB according to the embodiments as disclosedherein; and

FIG. 9 illustrates a user equipment (UE) according to the embodiments asdisclosed herein.

DETAILED DESCRIPTION

FIGS. 1A through 9, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein may be made without departing from the scope and spirit of thedisclosure. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

FIG. 1 through FIG. 9, discussed below, and the various embodiments usedto describe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

The term “couple” and its derivatives refer to any direct or indirectcommunication between two or more elements, whether or not thoseelements are in physical contact with one another. The terms “transmit,”“receive,” and “communicate,” as well as derivatives thereof, encompassboth direct and indirect communication. The terms “include” and“comprise,” as well as derivatives thereof, mean inclusion withoutlimitation. The term “or” is inclusive, meaning and/or. The phrase“associated with,” as well as derivatives thereof, means to include, beincluded within, interconnect with, contain, be contained within,connect to or with, couple to or with, be communicable with, cooperatewith, interleave, juxtapose, be proximate to, be bound to or with, have,have a property of, have a relationship to or with, or the like. Theterm “processor” or “controller” means any device, system or partthereof that controls at least one operation. Such a controller may beimplemented in hardware or a combination of hardware and software and/orfirmware. The functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely. Thephrase “at least one of,” when used with a list of items, means thatdifferent combinations of one or more of the listed items may be used,and only one item in the list may be needed. For example, “at least oneof: A, B, and C” includes any of the following combinations: A, B, C, Aand B, A and C, B and C, and A and B and C.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

In view of the specification, the terms wireless communication networkand network may be used interchangeably throughout the specification,and are to mean one and the same. The terms source cell and source nodemay be used interchangeably throughout the specification, and are tomean one and the same. The terms target cell and target node may be usedinterchangeably throughout the specification, and are to mean one andthe same.

Definitions for other certain words and phrases are provided throughoutthis disclosure. Those of ordinary skill in the art should understandthat in many if not most instances, such definitions apply to prior aswell as future uses of such defined words and phrases.

Aspects, features, and advantages of the disclosure are readily apparentfrom the following detailed description, simply by illustrating a numberof particular embodiments and implementations, including the best modecontemplated for carrying out the disclosure. The disclosure is alsocapable of other and different embodiments, and its several details canbe modified in various obvious respects, all without departing from thespirit and scope of the disclosure. Accordingly, the drawings anddescription are to be regarded as illustrative in nature, and not asrestrictive. The disclosure is illustrated by way of example, and not byway of limitation, in the figures of the accompanying drawings.

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a “beyond 4G network” or a“post LTE system.”

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission coverage, the beamforming, massive multiple-inputmultiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques and the like arediscussed in 5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud radioaccess networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul communication, moving network,cooperative communication, coordinated multi-points (CoMP) transmissionand reception, interference mitigation and cancellation and the like.

In the 5G system, hybrid frequency shift keying and quadrature amplitudemodulation (FQAM) and sliding window superposition coding (SWSC) as anadaptive modulation and coding (AMC) technique, and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse codemultiple access (SCMA) as an advanced access technology have beendeveloped.

In general, with an increased number of users of wireless communicationnetwork, the need to provide undisrupted and high quality of service tothe users is of prime importance for the telecom industry.

The wireless communication network supports communication for aplurality of user equipments (UE). Each UE communicates with one or morebase stations via transmissions on forward link and reverse link. Theforward link (or downlink) refers to a radio link from the base stationsto the UE, and the reverse link (or uplink) refers to the radio linkfrom the UE to the base stations. In the wireless communication network,radio link monitoring (RLM) is a mechanism for the UE to monitor qualityof the downlink (DL) for determining if the radio link is good enough tocontinue transmission.

The base station of a source cell in which the UE is currently located,facilitates communications of the UE. Due to mobility, the UE may enterinto coverage area associated with another base station which may beable to serve the UE better. However, the UE needs to perform handoverprocedure from the base station serving the source cell to a new basestation. In conventional mobility procedures, when the UE receives ahandover command, the UE suspends the radio link monitoring (i.e., RLMtimer T310 is stopped). Further, the handover procedure towards a targetcell is initiated immediately on reception of the handover command fromthe wireless communication network. An aspect of improved mobilityrobustness during the handover procedure is conditional Handover (CHO)which is agreed to be supported on both long term evolution (LTE) andNew Radio (NR). In the CHO scenario, a candidate cell (or a potentialtarget cell) is configured to the UE using a CHO configuration receivedas part of the handover command and then the CHO execution is initiatedbased on the UE satisfying a network configured condition. Unlike theconventional handover procedures, the UE in the CHO does not perform thehandover execution immediately on receiving the handover command fromthe wireless communication network. Therefore, if the RLM is suspended(or if the T310 is stopped, if the T310 running), the UE may be forcedto be latched on to a weak cell without being able to recover and hencebecome inefficient. During the CHO execution, the UE however continuesto receive signals from a source cell based on a radio/RF capability. Ifthe RLM is performed (e.g., if the T310 is not stopped, if the T310running) during the CHO execution time, then the UE encounters a radiolink failure (RLF) in the wireless communication network.

Another aspect of the UE which needs to be addressed in order to achievehigher efficiency is reduction in power consumption by the UE. Thereduction in power consumption for the UE is achieved by use ofmechanisms like Discontinuous Reception (DRX), over heating assistanceetc. In LTE systems, the UE is configured to send power preferenceindication (PPI), which has a very generic purpose that the wirelesscommunication network interprets as the UE is requesting optimized powerconsumption. However, a scenario of a transition of the UE from a radioresource control (RRC) CONNECTED state to one of: an RRC IDLE state oran RRC INACTIVE state is based on the discretion of the wirelesscommunication network. There is no feedback from the UE and hence ahigher possibility of increased and inefficient power consumption by theUE.

According to existing standard specifications, there is no mechanism bywhich the UE can indicate to the wireless communication network thatradio resource control (RRC) connection can be released, therebyreducing a possible the power consumption. Even if there is no datatransfer ongoing with the UE, the wireless communication network stillmaintains the RRC connection for duration of an inactivity timer. Theinactivity timer is not defined in existing standard specification but aparameter maintained by the wireless communication network which isimplementation specific. However, all wireless communication networksuse the inactivity timer and do not release the RRC connectionimmediately in order to ensure that there are no frequent requests forthe RRC connection from the UE resulting is unnecessary powerconsumption.

Accordingly the embodiments herein disclose a method for executingconditional handover by UE in a wireless communication network. Themethod may include receiving an RRC reconfiguration message from asource cell of the wireless communication network. The RRCreconfiguration message may include a handover configuration anddetermining whether a conditional handover (CHO) configuration isprovided in the handover configuration. The CHO configuration mayinclude a plurality of conditions for performing the CHO and a pluralityof target cell configurations. Further, the method may includeperforming one of: continuing an RLM timer (180) and an RLM procedure onthe source cell, in response to determining that the CHO configurationis provided in the handover configuration; and stopping the RLM timerand suspending the radio link monitoring procedure on the source cell,in response to determining that the CHO configuration is not provided inthe handover configuration. The method may then include executing theCHO from the source cell to a candidate target cell of the plurality oftarget cells in the wireless communication network based on the CHOconfiguration

Referring now to the drawings and more particularly to FIGS. 1A through7C, where similar reference characters denote corresponding featuresconsistently throughout the figure, these are shown preferredembodiments.

FIG. 1A illustrates a system for executing a conditional handover (CHO)in a wireless communication network, according to the embodiments asdisclosed herein.

Referring to the FIG. 1A, the system for executing the CHO in thewireless communication network may include the UE (100), a source gNB(1000 a) of a source cell within the ambit of which the UE (100) islocated, a Target gNB (1000 b) of a candidate target cell and aplurality of target cells. The UE (100) may be mobile and may be in anRRC connected state with the source gNB. Due to the mobility, the UE(100) may move closer to a coverage area associated with the candidatetarget cell which provides better signal strength, and the UE (100)needs to execute a handover from the source gNB (1000 a) to the targetgNB (1000 b). Radio link monitoring (RLM) may be a continuous procedureperformed by the UE (100) to monitor quality of a downlink (DL) tocontinue transmission. The UE (100) may be indicated to execute thehandover by sending an RRC reconfiguration message from the source cell.

Unlike to the conventional methods and systems, in the proposed methodthe UE (100) may not initiate the handover procedure/CHO immediately onreception of a handover command from the wireless communication network.Also, the UE (100) may not suspend the RLM procedure on the source cell(i.e., RLM timer T310 is not stopped) and hence continue to be latchedto the source cell even when the handover procedure is initiated.

Therefore, the UE (100) may be not forced to be latched on to a weakcell without thereby providing better efficiency. Further, in theproposed method during the CHO execution, the UE (100) may suspend theRLM (i.e., RLM timer T310 is stopped, if the RLM timer T310 is running)during the CHO execution time which ensures that the UE (100) does notencounter a radio link failure (RLF) in the wireless communicationnetwork.

FIG. 1B illustrates a block diagram of the UE (100) for executing theCHO in the wireless communication network, according to the embodimentsas disclosed herein.

Referring to the FIG. 1B, the UE (100) can be, for example, a mobilephone, a smart phone, Personal Digital Assistant (PDA), a tablet, awearable device, or the like. In an embodiment, the UE (100) can includea communicator (120), a memory (140), a processor (160) and an RLM timer(180). The UE (100) may be in an RRC connected state.

In one embodiment, the processor (160) may include one or moreprocessors or other processing devices that control the proposedfunction, process, and/or method. Operation of the UE 100 may beimplemented by the processor (160).

In an embodiment, the communicator (120) may be configured to receive aRadio Resource Control (RRC) reconfiguration message from a source cellof the wireless communication network. The RRC reconfiguration messagemay include a handover configuration. The handover configuration may bea set of instructions used to configure parameters and settings of theUE (100) to enable the UE (100) to execute the handover from the sourcecell to a target cell. Further, the handover configuration may alsoinclude the target cell configuration that the UE (100) shall apply on acandidate target cell once handover procedure is successfully completed.

In another embodiment, the communicator (120) may be also configured toreceive an RRC Reconfiguration message comprising a configurationsetting. In the absence of the configuration setting, the UE (100) maybe incapable of sending a state transition indication to the wirelesscommunication network. The configuration setting may include informationto the UE (100) that the UE (100) is allowed to send state transitionrequest to the wireless communication network.

The memory (140) can include non-volatile storage elements. Examples ofsuch non-volatile storage elements may include magnetic hard discs,optical discs, floppy discs, flash memories, or forms of electricallyprogrammable memories (EPROM) or electrically erasable and programmable(EEPROM) memories. In addition, the memory (140) may, in some examples,be considered a non-transitory storage medium. The term “non-transitory”may indicate that the storage medium is not embodied in a carrier waveor a propagated signal. However, the term “non-transitory” should not beinterpreted that the memory (140) is non-movable. In some examples, thememory (140) may be configured to store larger amounts of informationthan the memory. In certain examples, a non-transitory storage mediummay store data that can, over time, change (e.g., in Random AccessMemory (RAM) or cache).

In an embodiment, the processor (160) may include a CHO determinationengine (162), an RLM management engine (164), a HO management engine(166), an RRC state transition management engine (168), a timermanagement engine (170) and a UE assistance info message managementengine (172).

In an embodiment, the CHO determination engine (162) may be configuredto determine that a conditional handover (CHO) configuration is providedin the handover configuration. The CHO configuration may include aplurality of conditions for performing the CHO and a plurality of targetcell configurations associated with the plurality of target cells. Theplurality of target cell configurations may be carried in the RRCreconfiguration message as an OCTET string. The CHO configuration may bea delta configuration which details changes that are required to acurrent source cell configuration in order to configure the target celland execute the handover i.e., the target cell configuration is thecombination of the current source configuration and the deltaconfiguration included in the CHO configuration. However, the sourcecell cannot alter the plurality of target cell configurations in the CHOconfiguration.

In an embodiment, the RLM management engine (164) may be configured tocontinue a radio link monitoring (RLM) timer (180) and a radio linkmonitoring procedure on the source cell on determining that the CHOconfiguration is provided in the handover configuration. The RLMmanagement engine (164) may be configured to stop the RLM timer (180)and suspend the radio link monitoring procedure on the source cell ondetermining that the CHO configuration is not provided in the handoverconfiguration. The RLM timer (180) may be a T310 timer. Further, the RLMmanagement engine (164) may receive an indication from the HO managementengine (166) to suspend the RLM timer (180) and the radio linkmonitoring procedure on the source cell when the condition for executingthe CHO is fulfilled, and suspend the RLM timer (180) and the radio linkmonitoring procedure on the source cell.

In an embodiment, the HO management engine (166) may be configured todetermine the condition for executing the CHO from the source cell to acandidate target cell of the plurality of target cells and determinethat the condition for executing the CHO is fulfilled. The condition forperforming the CHO may be determined and appended by the source cell tothe CHO configuration.

Further, the HO management engine (166) may be configured to indicate tothe RLM management engine (164) to suspend the RLM timer (180) and theradio link monitoring procedure on the source cell and execute the CHOfrom the source cell to the candidate target cell in the wirelesscommunication network based on the candidate target cell configuration.

In an embodiment, the RRC state transition management engine (168) maybe configured to enable a capability to trigger an RRC state transitionindication to the wireless communication network. The capability may beenabled by activating the condition to trigger the RRC state transitionindication based on the RRC Reconfiguration message which enables thecapability to send the UE assistance information for indicating RRCstate transition. The condition may be one of: a timer based thresholdand a counter based threshold. Further, the state transition managementengine (168) may be configured to determine that at least one conditionto trigger the RRC state transition indication to the wirelesscommunication network is satisfied. The activated condition based on thetimer threshold may be one of: determining that the UE (100) isexplicitly configured with a dataInactivityTimer; configuring aninactiveIndicationTimer when the UE (100) is not explicitly configuredwith the dataInactivityTimer; and determining that a threshold conditionas a percentage of time for one of: the dataInactivityTimer and theinactiveIndicationTimer is met when said timer is running. The activatedcondition based on the counter threshold may include determining adrxInactivityTimer is not started at least once on activating thetrigger condition and a configured number of DRX cycles is elapsedwithout one of transmission or reception between the UE (100) and thewireless communication network, wherein the drxInactivityTimer is partof an RRC_CONNECTED state DRX cycle configuration.

The configuring of the inactiveIndicationTimer when the UE (100) is notexplicitly configured with the dataInactivityTimer may includedetermining that the UE (100) is not explicitly configured with thedataInactivityTimer by the wireless communication network andconfiguring, by the UE (100), the UE (100) with theinactiveIndicationTimer. A condition to one of: start theinactiveIndicationTimer and re-start the inactiveIndicationTimer may besame as the condition to one of: start the dataInactivityTimer andre-start the dataInactivityTimer.

Further, the state transition management engine (168) may be configuredto switch to one of: an RRC IDLE and an RRC INACTIVE state from theRRC_CONNECTED state based on an RRL release message received from thewireless communication network.

In an embodiment, the UE assistance info message management engine (170)may be configured to determine whether a preferred RRC state of the UE(100) to switch from the RRC_CONNECTED state is available. Further, ondetermining that the preferred RRC state of the UE (100) to switch fromthe RRC_CONNECTED state is available, the UE assistance info messagemanagement engine (170) may be configured to append the preferred RRCstate of the UE (100) in the UE assistance information message which isthen sent to the wireless communication network. When the preferred RRCstate of the UE (100) is indicated in the UE assistance information, thepreferred RRC state of transition may be RRC_INACTIVE state. Ondetermining that the preferred RRC state of the UE (100) to switch fromthe RRC_CONNECTED state is unavailable, the UE assistance info messagemanagement engine (170) may be configured to send the UE assistanceinformation message to the wireless communication network without thepreferred RRC state of the UE (100). When the preferred RRC state of theUE (100) is not indicated in the UE assistance information, the statetransition may indicate one of: the RRC_INACTIVE state and an RRC_IDLEstate. The UE assistance information may be an indication to thewireless communication network to trigger the state transition from theRRC CONNECTED state.

Although the FIG. 1B shows the hardware elements of the UE (100) but itis to be understood that other embodiments are not limited thereon. Inother embodiments, the UE (100) may include less or more number ofelements. Further, the labels or names of the elements are used only forillustrative purpose and does not limit the scope of the disclosure. Oneor more components can be combined together to perform same orsubstantially similar function.

FIG. 2A illustrates a flow chart 200 a of a method for executing the CHOby the UE in the wireless communication network, according to theembodiments as disclosed herein.

Referring to the FIG. 2A, at step 202 a, the UE may receive the RRCreconfiguration message from the source cell of the wirelesscommunication network. For example, in the UE (100) as illustrated inthe FIG. 1B, the communicator (120) can be configured to receive the RRCreconfiguration message from the source cell of the wirelesscommunication network.

At step 204 a, the UE may determine whether the conditional handover(CHO) configuration is provided in the handover configuration. Forexample, in the UE (100) as illustrated in the FIG. 1B, the processor(160) can be configured to determine that the conditional handover (CHO)configuration is provided in the handover configuration.

At step 206 a, the UE may continue the radio link monitoring (RLM) timerand the radio link monitoring procedure on the source cell, in responseto determining that the CHO configuration is provided in the handoverconfiguration. For example, in the UE (100) as illustrated in the FIG.1B, the processor (160) can be configured to continue the radio linkmonitoring (RLM) timer and the radio link monitoring procedure on thesource cell, in response to determining that the CHO configuration isprovided in the handover configuration.

At step 208 a, the UE may stop the radio link monitoring (RLM) timer andsuspend the radio link monitoring procedure on the source cell, inresponse to determining that the CHO configuration is not provided inthe handover configuration. For example, in the UE (100) as illustratedin the FIG. 1B, the processor (160) can be configured to stop the radiolink monitoring (RLM) timer (180) and suspend the radio link monitoringprocedure on the source cell, in response to determining that the CHOconfiguration is not provided in the handover configuration.

At step 210 a, the UE may determine that the condition for executing theCHO from the source cell to the candidate target cell is fulfilled. Forexample, in the UE (100) as illustrated in the FIG. 1B, the processor(160) can be configured to determine that the condition for executingthe CHO from the source cell to the candidate target cell is fulfilled.

At step 212 a, the UE may suspend the RLM timer (180) and the radio linkmonitoring procedure on the source cell. For example, in the UE (100) asillustrated in the FIG. 1i , the processor (160) can be configured tosuspend the RLM timer (180) and the radio link monitoring procedure onthe source cell.

At step 214 a, the UE may execute the CHO from the source cell to thecandidate target cell in the wireless communication network based on thecandidate target cell configuration of the plurality of target cellconfiguration. For example, in the UE (100) as illustrated in the FIG.1i , the processor (160) can be configured to execute the CHO from thesource cell to the candidate target cell in the wireless communicationnetwork based on the candidate target cell configuration of theplurality of target cell configuration.

The various actions, acts, blocks, steps, or the like in the method maybe performed in the order presented, in a different order orsimultaneously. Further, in some embodiments, some of the actions, acts,blocks, steps, or the like may be omitted, added, modified, skipped, orthe like without departing from the scope of the invention.

FIG. 2B illustrates a flow chart 200 b of a method for triggering an RRCstate transition indication by the UE (100) in the wirelesscommunication network, according to the embodiments as disclosed herein.

Referring to the FIG. 2B, at step 202 b, the UE may receive the radioresource control (RRC) Reconfiguration message from the wirelesscommunication network. For example, the UE (100) as illustrated in theFIG. 1B the communicator (120) is configured to receive the radioresource control (RRC) Reconfiguration message from the wirelesscommunication network.

At step 204 b, the UE may enable to send the RRC state transitionindication to the wireless communication network based on theconfiguration setting received in the RRC Reconfiguration message. Forexample, the UE (100) as illustrated in the FIG. 1B the processor (160)is configured to enable the UE (100) to send the RRC state transitionindication to the wireless communication network based on theconfiguration setting received in the RRC Reconfiguration message.

At step 206 b, the UE may determine that at least one condition totrigger the RRC state transition indication to the wirelesscommunication network is satisfied. For example, the UE (100) asillustrated in the FIG. 1B the processor (160) is configured todetermine that at least one condition to trigger the RRC statetransition indication to the wireless communication network issatisfied.

At step 208 b, the UE may determine whether the preferred RRC state ofthe UE (100) to switch from the RRC_CONNECTED state is available. Forexample, the UE (100) as illustrated in the FIG. 1B the processor (160)is configured to determine whether the preferred RRC state of the UE(100) to switch from the RRC_CONNECTED state is available.

At step 210 b, in response to determining that the preferred RRC stateof the UE to switch from the RRC_CONNECTED state is available, the UEmay append the preferred RRC state of the UE in the UE assistanceinformation message. For example, the UE (100) as illustrated in theFIG. 1B the processor (160) is configured to append the preferred RRCstate of the UE (100) in the UE assistance information message.

At step 212 b, the UE may trigger the RRC state transition indication bysending the UE assistance information message to the wirelesscommunication network. For example, the UE (100) as illustrated in theFIG. 1B the processor (160) is configured to trigger the RRC statetransition indication by sending the UE assistance information messageto the wireless communication network.

At step 208 b, in response to determining that the preferred RRC stateof the UE to switch from the RRC_CONNECTED state is not available, theUE may loop to step 212 b.

The various actions, acts, blocks, steps, or the like in the method maybe performed in the order presented, in a different order orsimultaneously. Further, in some embodiments, some of the actions, acts,blocks, steps, or the like may be omitted, added, modified, skipped, orthe like without departing from the scope of the invention.

FIG. 3A illustrates a signaling diagram of a suspension of the RLM timer(180) by the UE (100) immediately on receiving the handover (HO)command, according to the embodiments as disclosed herein.

Referring to the FIG. 3A, at step 302 a, consider that the UE (100) isin the RRC connected state with the source gNB (1000 a). In the RRCconnected state, at step 304 a, the source gNB (1000 a) sends ameasurement configuration to the UE (100). Further, at step 306 a, theUE (100) sends measurement report to the source gNB (1000 a). Themeasurement report includes a current configuration associated with theUE (100). The UE (100) performs the RLM by estimating the downlink radiolink quality and compare the downlink radio link quality to presetthresholds Qout for monitoring the downlink radio link quality of thesource cell (Pscell) to detect a radio link failure (RLF). The presetthreshold Qout is defined as a level at which the downlink radio linkcannot be reliably received and shall correspond to the out-of-syncblock error rate (BLERout).

Further, the UE (100) measures a Block Error Rate (BLER) of a PhysicalDownlink Control Channel (PDCCH) during a predetermined time period.Further, at step 308 a, the UE (100) determines that the BLER dropsbelow the preset threshold (Qout) during the predetermined time periodand an out-of-sync indication is generated in a physical (PHY) layer.When a preset N310 number of successive out-of-sync indications arereported to the RRC layer by the PHY layer, the RLM timer (180) isstarted by the RRC layer (step 310 a).

At step 312 a, the source gNB (1000 a) sends the RRCReconfigurationmessage to the UE (100). In the conventional methods and systems, the UE(100) in response to receiving the RRCReconfiguration message, at step314 a, stops the RLM timer (180) on and at step 316 a, suspends the RLMprocedure. Further, at step 318 a, the UE (100) executes the handoverfrom the source cell to the target cell and at step 320 a, sends theReconfiguration complete message to the target gNB (1000 b).

However, the signaling in the CHO scenario may be similar to signalingin the HO scenario with some changes. The HO signaling for the CHOscenario may include some limitations such as:

-   -   1) Whether to support candidate target cells controlled by        different target nodes (which may affect radio signaling)    -   2) Whether to support candidate target cells on different        carrier frequencies/MOs (which may affect the CHO configuration        to be provided for the candidate)    -   3) Whether same handover configuration parameters can be        signaled by the target node at the CHO preparation. Further, the        CHO configuration may include only the most essential parameters        which need to be updated in the source cell configuration.

In order to achieve the CHO, the configuration parameters are typicallyconfigured by the source node (source cell) and the target node (targetcell) at the CHO configuration (i.e., in signaling towards the UE (100))and are assumed to be known. Further,

-   -   1) the source node controls the CHO candidates which are to be        configured and therefore, the source node sets:        -   a) the CHO condition i.e., something based on A3 or A5            (possibly only need to indicate offset as based on the            condition for measurement used to add the CHO candidate)        -   b) the validity timer i.e., a timer upon the expiry of which            the UE (100) releases the CHO configuration (i.e., the            source node manages the plurality of the CHO candidates but            may not always succeed in releasing the at least one CHO            candidate of the plurality of CHO candidates)        -   c) Further, the UE (100) should be allowed to set a            different value for each of the CHO candidate, at least for            the CHO condition.    -   2) The target node sets the configuration to be used when the UE        (100) moves to the CHO from an initial access. However, some of        the important considerations with respect to the configuration        by the target node include:        -   A. reconfigurationWithSync is the most essential            configuration parameter and particularly:            -   a) contention-free based random access (CFRA) resources                (e.g. for all wide/cell specific beams, given delay                between the CHO configuration and execution)            -   b) PCell (dedicated and common) configuration            -   c) T304 (to guard the actual CHO execution phase i.e.,                started after the CHO condition is achieved)        -   B. the network can include other configuration such as for            example: radioBearerConfig, RLC bearerConfig, MAC config,            measConfig. However, to avoid the need to reconfigure, the            network may only include the most essential parameters in            the CHO configuration. The configuration which may not be            essential are temporarily suspended/deactivated and then            resumed/re-activated upon the first subsequent            reconfiguration (i.e., when the network can modify)            -   a) measConfig may need to be changed i.e., to continue                measurements on the new primary frequency (for the case                of inter-frequency CHO)            -   b) If multiple CHO candidates are configured, then the                other configuration may not be the same for all the                candidates i.e., for example, when the candidates are on                different frequencies (different measConfig) or                controlled by the different target nodes (with different                capabilities/typical settings).        -   C. The CHO configuration is assumed to be the delta            configuration compared to the current source configuration            (i.e., source config as used at the time of the CHO            configuration).

Further, after initiating the CHO configuration, the source node shouldbe able to modify the source configuration as:

-   -   I. Some reconfiguration cannot be postponed. Such as for example        addition of a QoS flow or DRB upon activation of a service with        specific QoS requirements    -   II. Some of the source reconfigurations affect the configuration        to be used after the execution of the CHO such as for example if        new QoS flows or DRBs are added, they should continue after the        CHO configuration i.e., affect the CHO configuration.        Therefore, the specification changes for the CHO may be limited        in the existing methods and systems.

In the proposed method, the basic starting points for performing theconditional handover may be as follows:

-   -   a) the source node (at least) sets the CHO condition and the        source node should be able to configure different values for the        different candidates.    -   b) determine whether the CHO target cell configuration should        cover parameters other than the reconfigurationWithSync for        example parameters such as: measConfig, radioBearerConfig and/,        L2 config or not cell specific L1 config. Further, in case the        CHO target cell configuration should cover the parameters, then        determine whether the target node should be able to set        different values for the configuration parts for the different        CHO candidates.

The method for signaling of the configuration changes when the sourcereconfiguration affects the CHO configuration may require that thesource node should be able to modify the source configuration afterhaving initiated the CHO configuration and in some cases theconfiguration to be used in the CHO candidate after the CHO execution isaffected.

Consider a scenario where the source node initiates the configurationchange that should continue after the CHO execution i.e., for exampleaddition of a QoS flow or DRB. As indicated previously, we assume theCHO configuration is indicated by signaling the delta compared to thecurrent source configuration (i.e., at the time of the CHOconfiguration).

-   B. To ensure the change of the source cell configuration continues    after the CHO execution, the source node could either indicate the    target cell of the CHO by signaling:    -   a) Delta compared to the updated source cell configuration    -   b) Delta compared to the previous CHO configuration        option a) is the simplest, as the source cell configuration is        same as used at the initial CHO configuration.

Further, another issue is whether the change to the source cellconfiguration and the target cell configuration should be signaledtogether (i.e., in the same message), or can the signaling be doneseparately (i.e., in different messages):

-   -   1) When signaling the changes to the source cell configuration        and the target cell configuration together:        -   a) The changes will succeed/fail jointly (+)        -   b) Will require some means to distinguish which            configuration part concerns with the source CHO            configuration and which part concerns with the target CHO            configuration    -   2) When signaling the changes to the source cell configuration        and the target cell configuration separately:        -   a) There may be collision problems i.e., the UE (100)            executes the CHO in-between the two messages. This may apply            even if the two messages are transmitted together (as            processing is done sequentially)

In an embodiment of the proposed method, the CHO configuration may beindicated by signaling the delta compared to the current sourceconfiguration i.e., both at the initial setup and upon reconfigurationof the CHO configuration.

In another embodiment, the conditional handover may support simultaneousreconfiguration of the source cell and the CHO configuration i.e.,together within the same message.

Further, another issue is about how to signal the source cellconfiguration and the target cell configuration parts i.e., for exampleusing a container/field. Conventionally, both the source cell and thetarget cell generate some configuration parameters that are to beprovided to the UE (100). There are different ways to signal theconfiguration parameters to the UE (100) such as:

-   A. A regular reconfiguration message may be used, including the    parameters generated by the source node and by the target node;    i.e., either    -   A1: The source node may forward the parameters generated by the        source node to the target node, which generates the Uu message        including these source controlled parameters    -   A2: The source node may decode the message generated by the        target and adds the parameters-   B. A container may be added to the reconfiguration message i.e., to    carry the configuration generated by the target node (alike in case    of Inter Radio Access Technology handover (IRAT HO))    -   B.1: Octet string/container may carry the Reconfiguration        message    -   B.2: Octet string/container may carry an IE including a subset        of the fields of the Reconfiguration message.

Further, when the container is added to the reconfiguration message, thesupport to signal the change of the source cell configuration and theCHO candidate configuration together is easier. Moreover, the fieldswhich concern the CHO configuration are clearly defined. However, whenthe regular reconfiguration message is used to signal the configurationparameters to the UE (100), the procedure is not straightforward. Forexample, there may be a need to introduce specific fields for the CHOcandidate configuration e.g. a separate spCellConfig, measConfig.Further, the usage of the regular reconfiguration message may requirespecifying of the fields that the target cell can set/change as part ofthe CHO configuration i.e., it limits network implementation.

The option B.1 is preferable and avoids the need to discuss detailsabout which fields can be set as part of the CHO configuration and hencein the proposed method the octet string/container is added to thereconfiguration message to carry the CHO configuration generated by thetarget node (alike in case of IRAT HO). This octet string carries aReconfiguration message.

Furthermore, another issue is about signaling the target configurationfor multiple CHO candidates for example sending individual message percandidate. Also, the issues of how to signal the CHO configuration whenthere are multiple CHO candidates. The available techniques includesignaling using:

-   -   I: A single message    -   II: A message per CHO candidate

When the single message is used to signal the CHO configuration to themultiple CHO candidates, the option to include multiplespCells/reconfigurationWithSync fields needs to be added. The sameapplies for other fields which value may differ per CHO candidate.

The usage of separate message per CHO candidate to signal the CHOconfiguration to the multiple CHO candidates, may provide a moreflexible signaling structure:

-   -   1) The specification changes will be limited to introducing        multiple octet string containers.    -   2) This option can support the CHO candidates on different        target nodes    -   3) The signaling is future proof

Further, the issue relates to the outcome of the RAN2 being requested toreview and confirm the general starting points. The issue also relatesto adding the octet string/container to the reconfiguration message tocarry the CHO configuration that touches the same aspect of whether ornot the signaling should be flexible or restrictive.

In another embodiment of the proposed method, a list of octetstring/containers may be added to the reconfiguration message, whereeach of the octet string/container is carrying the CHO configuration ofa single CHO candidate as generated by the target node (alike in case ofIRAT HO). Each octet string may carry a Reconfiguration message.

The usage of separate message per CHO candidate to signal the CHOconfiguration to the multiple CHO candidates may result in duplicatetransfer of other configuration that is same for multiple candidates.However, the duplication of the configuration may be avoided for exampleby an indication that the value is same as of another entry in the list.

According to the earlier embodiment, source (at least) may set the CHOcondition and signal the CHO condition per candidate. There may be 2different ways to provide the CHO condition per candidate:

-   -   II.1: The source node includes a CHO candidate list field, for        these source controlled parameters (e.g. condition)    -   II.2: The source node forwards the parameter to the target node,        which includes the CHO condition in the target generated message        (for each candidate)

Option II.1 may be somewhat more in the spirit of the proposed method.On the other hand, from the UE (100) perspective it may be simplest tonot have a separate CHO candidate list field to be associated with atarget generated container. Hence preference may be for option II.2

Therefore, in an embodiment of the proposed method, the source node mayforward the CHO candidate parameters that it controls to the targetnode, and the target node may include it in the target generated message(per each candidate).

Another issue which needs to be addressed is about when to send the CHOcomplete message by the UE.

The techniques available may include:

-   -   1. Upon the CHO execution i.e., following initial access in the        candidate cell (as done for the regular HO scenario), and    -   2. Immediately i.e., upon the CHO configuration (in which case        some other signal may be needed to be sent upon the CHO        execution).

In order to select the technique for sending the CHO complete message bythe UE (100), the concerns about the action required upon the CHOconfiguration including the case in which the UE (100) is unable tocomply with the CHO configuration needs to be addressed. Further, theassumption is that the UE (100) performs re-establishment, but the UE(100) may perform the action either upon the CHO configuration or uponthe CHO execution. Also, there may be no real benefit in delayingre-establishment until the CHO execution. If however the UE (100) isable to comply, there seems no real need for an RRC message to confirmreceipt and proper comprehension (i.e., L2 ACK seems sufficient); i.e.,option 1, that is aligned with the regular HO seems sufficient.

Consider a scenario when the reconfiguration message also includes thechange of the source cell configuration. Then, the UE may return thecomplete message to confirm the source cell reconfiguration. Therehowever seems no need to include any indication regarding the CHOreconfiguration.

In an embodiment, the UE may return a CHO complete message upon theexecution of the CHO i.e., following initial access in the candidatecell (as for regular HO). If the message including the CHO configurationalso includes a source cell reconfiguration, the UE may immediatelyreturn a complete message (without explicit confirmation ofreceipt/comprehension of the CHO reconfiguration). In case ofnon-comprehension of the CHO configuration, the UE may immediatelyperform re-establishment (i.e., not delayed until the CHO execution).

In the conventional radio link monitoring procedure performed duringmobility, currently available in the LTE and the NR, the RLM may besuspended (RLM timer (180) T310 is stopped, if the T310 is running)immediately on reception of the HO command from the network. The HOprocedure may be performed when the signal quality of the source cellbecomes weak and the signal quality of a neighbouring cell becomestronger thereby making the neighbour cell better suited to serve theUE. As a result, the HO command may be normally signalled to the UE whenthe signal condition of the source cell is weak. Additionally, there isgood probability that the UE fails to perform handover due to theinability to successfully receive the HO command from the network due todeterioration of the serving cell signal conditions. In order to reducehandover failures caused due to the failure in receiving the HO command,early handover provisioning using CHO mechanisms are also beingdiscussed in RAN2. Further, the HO command may be signalled to the UE(100) when the serving cell signal condition is weak and there is apossibility of the HO failure due to the inability to receive themessage successfully.

Consider that the UE (100) is configured with enhanced make before break(eMBB) handover then the UE (100) is expected to synchronize to thetarget cell and initiate random access procedure while the connection tothe source cell is still active, although the signal condition may stillbe weak. There may be two distinct possibilities of the handover failurei.e., the source cell may encounter RLF or the target cell may encounterhandover failure. However, the handover command may be provided to theUE (100) when the serving cell signal conditions are detected to begetting weaker and that the neighbour cell (target cell for handover)has a better signal conditions and thereby more suitable to serve the UE(100). Therefore, the probability of encountering the radio link failureon the source cell may be higher as compared to that of handover failureon the target cell. Further, the probability of encountering the radiolink failure on the source cell may be higher as compared to that ofhandover failure on the target cell in the eMBB handover.

Therefore, if the UE (100) continues to perform radio link monitoring onthe source cell during HO execution period, it is possible that the UE(100) declares the RLF on the source cell due to which the UE (100) hasto abort the HO execution on the target cell and will result in the UE(100) performing the re-establishment procedure. The prematuresuspension of the HO execution can be avoided if the UE (100) does notinitiate the re-establishment procedure if the radio link failure isdetected on the source cell while the handover execution on the targetcell is still in progress, thereby allowing the UE (100) to continuewith the handover execution on the target cell without any interruption.Alternately, the radio link monitoring on the source cell can besuspended the when handover command is received. However, both themethods may be performed to achieve a similar objective and one does notappear to be better than the other.

Unlike to the conventional methods and systems, in the proposed methodthe radio link monitoring is suspended on reception of the HO command asthe same is in-line with behaviour defined in specification for existingmobility mechanisms. Further, the result of suspending the radio linkmonitoring on the source cell on reception of the HO command from thenetwork is similar to that of the UE (100) not initiating there-establishment when the RLF is declared on the source cell while theHO execution to the target cell is in progress.

In an embodiment, the UE (100) may suspend the radio link monitoring onthe source cell on receiving the HO command which includes the makebefore break indication. The above described UE (100) behaviour isillustrated in the FIG. 1. This can further be applied to any handovertype wherein the UE (100) executes immediate handover upon reception ofthe HO command from the network.

Consider the scenario when the UE (100) is configured with theconditional handover (CHO). In case of the CHO mechanism, the HO commandmay be expected to be received much earlier than the intended time ofthe actual execution of the handover. The HO command may be sent inadvance in case of the CHO to avoid handover failure due to the UE (100)not receiving the handover command successfully. In such cases thesuspension of the radio link monitoring on the reception of the HOcommand from the network may not be right. Therefore, the UE (100) maycontinue the radio link monitoring on the source cell when the CHO isconfigured to the UE (100). When the handover is being executed by theUE (100) on the target cell upon meeting the condition defined in the HOcommand, then the UE (100) should suspend the radio link monitoring onthe source cell i.e., stop T310 (if running). If the RLM is continuedwhen UE (100) initiates the handover execution on the target cell thereis a risk of facing the RLF on the source cell resulting in thepremature failure of the handover to the target cell. Therefore, theradio link monitoring on the source cell should be suspended when thehandover execution is initiated upon the condition defined in the HOcommand is met.

In an embodiment, when the UE (100) is configured with the conditionalhandover (CHO), the radio link monitoring on the source cell may becontinued when the handover command is received from the network. Inanother embodiment, when the UE (100) is configured with the conditionalhandover (CHO), the radio link monitoring on the source cell may besuspended when the UE (100) initiates the handover execution to thetarget cell when the condition configured in the handover command ismet. In an embodiment, the UE (100) may support one of the LTE RAT andthe NR RAT.

FIG. 3B illustrates a signaling diagram of the continuation of the RLMtimer (180) on the source cell till the execution of the HO commandbased on the CHO configuration, according to the embodiments asdisclosed herein.

Referring to the FIG. 3B in conjunction with the FIG. 3A, the steps 302b to 312 b in the FIG. 3B may be substantially the same as steps 302 ato 312 a in the FIG. 3A, and, thus repeated description is omitted. Atstep 314 b, unlike to the conventional methods and systems, the UE (100)may continue the T310 timer on receiving the HO command and may also atstep 316 b continue the RLM procedure on the source cell. Further, atstep 318 b, the UE (100) may monitor for satisfying the conditionprovided in the HO command for performing the conditional handover. Atstep 320 b, in response to determining that the condition for performingthe conditional handover is satisfied, the UE (100) may suspend the RLM(stop T310 if running) on the source cell when the HO executionprocedure is initiated. Further, at step 322 b, the HO executionprocedure may be completed and at step 324 b, the UE (100) may send theReconfiguration complete message to the target gNB (1000 b).

When the UE (100) is configured with the enhanced make before break(eMBB) and the conditional handover (CHO) for the same target cell, thenthe MBB/eMBB configuration may be provided in addition to the CHOcriteria in the HO command. In such HO type, since the HO executioncriteria are included, the HO command may be received earlier in timethan the need to perform the HO execution. During this time, the servingcell condition may be expected to be sufficient to serve the UE (100)and the neighbour cells may not be suitable to handle the UE (100) undercurrent signal conditions. If the radio link monitoring for the sourcecell is suspended in such cases, then the UE (100) may get locked on tothe serving cell without having a mechanism to recover from the linkdegradation and related issues when the UE (100) moves towards a celledge or out of coverage of the serving cell. Therefore, if the makebefore break (MBB/eMBB) handover in combination with the CHO isindicated, the UE (100) may need to continue the RLM procedure on theserving cell when the HO command is received.

However, the HO execution may be initiated by the UE (100) only when theCHO condition is met where the UE (100) follows the MBB/eMBBconfiguration provided in the HO command. When the CHO condition is met,then the serving cell signal conditions may start degrading and theneighbour cell may become better suited to serve the UE (100) further.In such cases, the probability of the radio link failure on the sourcecell may be expected to be higher than the probability of the HO failureon the target cell as the target cell has satisfied the conditionrequired for performing the HO.

In an embodiment, the UE (100) configured with a HO type that combinesmake before break handover configuration and the CHO condition, the UE(100) suspends the radio link monitoring on the source cell when the HOexecution to the target cell is initiated in the event when thecondition configured in the HO command is met.

In another embodiment, when the UE (100) is configured with a HO typethat combines make before break configuration and the CHO condition, theradio link monitoring on the source cell may be continued by the UE(100) upon reception of the HO command from the network.

In yet another embodiment, when the UE (100) is configured with a HOtype that combines the enhanced make before break handover configurationand the CHO condition, the radio link monitoring on the source cell maybe continued by the UE (100) upon reception of the HO command from thenetwork.

In yet another embodiment, when the UE (100) is configured with a HOtype that combines the enhanced make before break configuration and theCHO condition, the radio link monitoring on the source cell may besuspended by the UE (100) when the HO execution to the target cell isinitiated in the event when the condition configured in the HO commandis met. Thus the UE (100) behaviour is illustrated in the FIG. 3B.

Therefore, unlike to the conventional methods and systems, in theproposed method, whenever the condition for performing the CHO isprovided, or whenever a condition is specified along with any HOcommand, the RLM monitoring on the source cell is continued even afterthe HO command is received from the network. The RLM on the source cellis suspended only once the HO execution to the target cell is initiated(when the condition in the HO command is satisfied for the UE (100)).

FIG. 4 illustrates a flow chart 400 of the radio link monitoring duringthe HO execution, according to the embodiments as disclosed herein.

In an embodiment, consider the RLM monitoring for a NR UE which iscontrolled as described in the FIG. 4. The UE may be the NR UE. At step402, when the NR UE is in the RRC CONN state, the MR (MeasurementReport) may be sent to the source cell and at step 404, the RRC CONNstate procedure may be performed. Further at step 406, the NR UE maydetermine whether the HO command is received from the network. Inresponse to determining that the HO command is not received at the step406, the NR UE may loop back to the step 404. In response to determiningthat the HO command is not received at the step 406, the NR UE at step408 may determine whether the HO command includes the CHO configuration.

In response to determining that the HO command includes the HO typeindicated in the Rel 15 HO or Rel 16 MBB/eMBB HO, at step 418, the NR UEmay stop the RLM timer (180) i.e., the T310 timer immediately onreception of the HO command and suspends the RLM on the source cell.

In response to determining that the HO command includes the HO typeindicated as one of: the conditional handover criteria, or a combinationof the Rel 15 HO or the Rel 16 MBB/eMBB HO and the conditional handovercriteria, then the NR UE at step 410, may continue the RLM timer (if theT310 timer is already running) and continues the RLM procedures on thesource cell.

Further at step 412, the NR UE may determine whether the conditionalhandover criteria is satisfied. In response to determining that theconditional handover criteria is not satisfied, the NR UE may loop tothe step 410. In response to determining that the conditional handovercriteria is satisfied, the NR UE may initiate the HO execution at step414 and also suspend the RLM for the source cell (i.e., the T310 timeris stopped, if the T310 timer running). Further, at step 416, the NR UEmay execute the handover and switches from the source cell to thecandidate target cell.

In an embodiment, the UE may be the LTE UE. At step 408, when the HOtype indicated to the LTE UE is Rel 16 eMBB HO or any pre-Rel16 HO, thenat step 422, the UE shall, stop the T310 immediately on reception of HOcommand (suspend RLM on source cell).

At step 408, when the HO type indicated to the LTE UE is one of:conditional handover criteria and a combination of the Rel 16 eMBB orany of the pre-Rel16 HO and the conditional handover criteria, then atstep 410, the UE shall continue the T310 timer (if the T310 timer isrunning) and the RLM procedures on the source cell. Further, when the HOexecution begins in the event conditional handover criteria are met (atstep 412), the UE may suspend the RLM for the source cell (T310 timerstopped if the T310 timer running) (as indicted in the step 414).

FIG. 5A illustrates a signaling diagram of pro-active neighbour cellpreparation for re-establishment to perform handover failure recovery,according to the embodiments as disclosed herein.

FIG. 5B illustrates a signaling diagram of target cell preparation forthe HO execution, according to the embodiments as disclosed herein.

Consider a scenario where the UE (100) encounters the radio link failure(RLF). In response to the RLF, the UE (100) may perform the cellselection procedure in order to select a suitable cell to re-establishthe connection with the network. If the suitable cell is selected whilethe timer T311 is still running, then the UE (100) may attempt tore-establish the RRC connection, otherwise the UE (100) may transit toan idle state. Further, the UE (100) may decide the target cell for there-establishment based on the cell search order and the cell signalquality.

The latency produced in the phase of handover failure recovery can bereduced by the network, by assisting the UE (100) with the preparationof the cell(s) on which the UE (100) can perform the re-establishment.However, the assistance information may become useful only if the sourcecell (on which the RLF is being triggered) has already prepared thepotential target cell (on which the UE (100) can perform there-establishment) with the UE (100) context prior to the UE (100)encountering the RLF. Therefore, the UE (100) may inform the network inadvance via the measurement report about the presence of a certainneighbour cells which in turn allows the network to proactively preparethe neighbour cell to accommodate for the potential re-establishmentfrom the UE (100). The preparation of the target cells for there-establishment may include: at step 502 a, the UE (100) may receivethe measurement configuration from the source gNB (1000 a). At step 504a, the UE (100) may send the measurement report to the source gNB (1000a). Further, the source gNB (1000 a) may communicate with the target gNB(1000 b) and prepare the target cell for performing there-establishment. Further, the target gNB (1000 b) may send the RRCReconfiguration with the list of target cells which can be used forre-establishment.

The sequence of procedures and the signalling involved in order tosupport early preparation of the target cells for the re-establishmentare similar to that of the handover signalling (as described in steps502 b-508 b except for the step 506 b where the source gNB (1000 a)prepares the target cell for performing the handover). Therefore, thenetwork need not assist the UE (100) with the list of prepared cells.Instead, the network may rather choose to perform the handover.

FIG. 6 illustrates a flow chart 600 of the cell selection prioritization(order) when the UE (100) attempts the re-establishment of theconnection with the wireless communication network, according to theembodiments as disclosed herein.

In another embodiment, the target cell may be selected for handoverfailure recovery, for example, by prioritizing the cells for which themeasurement report is sent to the source cell. On receiving themeasurement report from the UE, the source cell may have prepared thetarget cells with the UE context. The UE may leverage that the sourcecell has prepared the target cells with the UE context and attempt forthe failure recovery on the target cells. Further, when the UE selects asuitable cell for performing the re-establishment of the RRC connection,if the T311 is still running on the UE, then the UE may initiate therandom access procedure and the T301 may be stared. The T301 may be usedin order to monitor and control the success/failure of the random accessprocedure and hence cannot be optimized.

Simultaneously, the target cell may try to fetch the UE context from thesource cell after the successful reception of the re-establishmentrequest from the UE. The reduction in the UE context retrieval time ispossible if the UE (100) attempts the re-establishment on the cells forwhich the measurement report is sent to the source cell. On receivingthe measurement report from the UE (100), the source cell may havesuccessfully prepared the target cell prior to the UE (100) encounteringthe radio link failure. The scenario can be handled if the UE (100)follows the prioritized cell selection procedure.

In the prioritized cell selection procedure, during the handover failureor the radio link failure recovery procedure, a higher priority isprovided for the cell for which a measurement report is sent to thesource cell prior to the RLF. Therefore, the UE (100) may attempt tore-establish the connection to the cells which may already be preparedfor the UE based on the measurement report which is previously sent tothe source cell. Further, the next higher priority may be given to thecells that were detected when on the source cell but for which themeasurement report is not triggered. The re-establishment may beattempted for the next higher priority cells as there is a highprobability that the UE is still in vicinity of the detected cells whileattempting to perform the re-establishment. Further, the next prioritymay be provided to all the remaining other cell.

Sequence of procedures involved in selecting target cell for handoverfailure or radio link failure recovery is illustrated in the FIG. 6. Atstep 602, the UE which is in the RRC CONN state, may perform the RLMprocedure. At step 604, the UE may determine whether the RLF isdeclared. In response to determining that the RLF is not declared, theUE may continue the RLM procedure. In response to determining that theRLF is declared, at step 606, the UE may determine whether themeasurement report is sent on the source cell.

On determining that the measurement report is sent on the source cell,at step 608, the UE may attempt the target cell selection on the targetcells for which the MR was sent. Further, at step 610, the UE maydetermine whether a suitable target cell (candidate target cell) isfound to which the UE can perform the re-establishment. In response todetermining that the suitable target cell is found, at step 620, the UEmay select the target cell and performs the re-establishment procedure.

In response to determining that the suitable target cell is not found,at step 612, the UE may attempt the target cell selection on the targetcells that were detected and measured in the RRC CONN state. Further, atstep 614 a, the UE may determine again whether the suitable target cellis found to which the UE can perform the re-establishment. In responseto determining that the suitable target cell is not found, at step 616,the UE may attempt target cell selection on other target cells and maythen again check whether the suitable target cell is found at step 618.At step 614 and step 618, in response to determining that the suitabletarget cell is found, the UE may select the target cell and performs there-establishment procedure (step 620).

FIG. 7A illustrates a signalling diagram of a method of performing theUE controlled state transition from RRC_CONNECTED state to RRC_INACTIVEstate as on a configured threshold, according to the embodiments asdisclosed herein.

FIG. 7B illustrates a signalling diagram of a method of performing theUE controlled state transition from the RRC_CONNECTED state to theRRC_INACTIVE state transition as on a configured timer, according to theembodiments as disclosed herein.

FIG. 7C illustrates a signalling diagram of a method for performing theUE autonomous state transition from the RRC_CONNECTED state to anRRC_IDLE state as on a configured timer, according to the embodiments asdisclosed herein.

In general, 3GPP is studying methods to reduce power consumption in theUE (100) and make the UE (100) more power efficient. In general, the UE(100) consumes maximum power when the UE (100) is in the RRC CONN Stateand the UE (100) consumes least power when the UE (100) is in one of:the RRC IDLE state and the RRC INACTIVE state. Therefore, in order toimprove power efficiency the UE (100) can be moved to one of: the RRCIDLE state and the RRC INACTIVE state from the RRC CONN State when thereis no data transfer expected.

Referring to the FIG. 7A, at step 702 a, the UE (100) may be in the RRCconnected state and at 704 a, the UE (100) may share the UE capabilityexchange indicating support of the UE assisted transition to INACTIVEstate. At step 706 a, the RRC Reconfiguration including theconfiguration to allow the UE (100) to send the indication for thetransition from the RRC CONN state to the RRC INACTIVE state isconducted. Further, at step 708 a, the UE (100) may monitor thecondition of one of: the timer and the counter to trigger the RRCINACTIVE state transition request. The timer may be for example theDataInactivityTimer. Further, at step 710 a, the UE (100) may determinethat the condition to request the network for the state transitionsatisfied and at step 712 a, the UE (100) may send the indication to thewireless communication network for the state transition. Further, the inresponse to the indication for the state transition, the gNB (1000) ofthe wireless communication network may send the RRC Release message withoptional resume id.

In an embodiment, the UE (100) in the RRC connected state may be allowedto send the indication for the state transition, if the UE (100) isconfigured with the dataInactivityTimer.

In an embodiment, if the datainactivityTimer is running, the UE (100) inthe RRC Connected state may monitor a condition such as for example aninactiveIndicationThreshold condition (step 708 a) to trigger the statetransition indication. On determining that theinactiveIndicationThreshold condition is met (step 710 a), the UE (100)may trigger the state transition indication to the network (step 712 a)as illustrated in the FIG. 7A. Further, the inactiveIndicationThresholdcondition may be specified as a percentage or the datainactivityTimer orin terms of C-DRX cycles while the datainactivityTimer is running.

In an embodiment, the state transition indication may be a request tothe network to send the UE (100) from the RRC Connected state to the RRCINACTIVE state.

In an embodiment, after triggering the state transition indication, uponexpiry of the datainactivityTimer the UE (100) may move to the RRC IDLEstate.

In another embodiment, the UE (100) may be allowed to send theindication for the state transition if the UE (100) is explicitlyconfigured with the inactiveIndicationTimer.

In an embodiment, a condition to start/re-start theinactiveIndicationTimer may be same as the datainactivityTimerregardless of whether the datainactivityTimer is configured. Therefore,referring to the FIG. 7B, the UE (100) in the RRC Connected state (702b) may trigger the state transition indication to the network (712 b),when the inactiveIndicationTimer expires (710 b), as illustrated in theFIG. 7B.

Referring to the FIG. 7C, steps 702 c to 712 c may be substantially thesame and hence repeated description is omitted. At step 716 c, the RRCRelease message with resume id may be not received by the UE (100). Inan embodiment, after triggering the state transition indication, the UE(100) may start the waitTimer and upon expiry of the waitTimer (step 716c), the UE (100) may move to the RRC IDLE state as illustrated in theFIG. 7C.

In another embodiment, the UE (100) may be allowed to send theindication for the state transition, if the UE (100) is explicitlyconfigured with inactiveIndicationTimer in addition the UE (100) isconfigured with dataInactivityTimer.

In an embodiment, the condition to start/re-start theinactiveIndicationTimer may be same as datainactivityTimer.

In an embodiment, if the datainactivityTimer is running, the UE (100) inthe RRC Connected state may trigger the state transition indication tothe network, when the inactiveIndicationTimer expires.

In an embodiment, after triggering the state transition indication, thewaitTimer may starts and upon expiry of either the waitTimer ordataInactivityTimer whichever is earlier, the UE (100) may move to theRRC IDLE state.

Unlike to the conventional methods and systems, the proposed method mayallow the UE (100) to inform the network about the UE capability torequest or assist the serving gNB for the RRC CONN to the RRC INACTIVEstate transition. On receiving the UE capability, the network may chooseto one of: allow the UE (100) to request state transition when requiredand not allow the UE (100) to request state transition when required. Ifthe serving gNB chooses to allow the UE (100) to request for the statetransition, then the UE (100) may monitor the conditions and criteriawhich can eventually trigger the request to network.

In an RRC message (for example: RRCReconfiuration message), the networkmay provide the UE (100) with the necessary configuration required torequest for the state transition. Therefore, the RRC message with theconfiguration required to request for the state transition may allow theUE (100) to monitor the required conditions and trigger indication tothe network for the state transition from the RRC CONN to the RRCINACTIVE needed. The network may provide the configuration for one of:triggering indication to network, requesting state transition/connectionrelease, as a timer based configuration or a counter basedconfiguration. In current release 15 specifications, a dataInactivityTimer is used to allow the UE (100) for implicit transition to the RRCidle state.

The details of the timer handling may be as provided below:

-   -   start or restart dataInactivityTimer:        -   if any MAC entity receives a MAC SDU for DTCH/DCCH/CCCH            logical channel.        -   if any MAC entity transmits a MAC SDU for DTCH/DCCH logical            channel    -   dataInactivity Timer Expiry:        -   indicate the expiry of the dataInactivityTimer to RRC    -   RRC handling on receiving indication of dataInactivityTimer        expiry:        -   perform the actions upon going to RRC_IDLE, with release            cause ‘RRC connection failure’

MAC-CellGroupConfig ::=  SEQUENCE {  drx-Config   SetupRelease {DRX-Config } OPTIONAL, -- Need M  schedulingRequestConfig  SchedulingRequestConfig OPTIONAL, -- Need M  bsr-Config  BSR-ConfigOPTIONAL, -- Need M  tag-Config  TAG-Config OPTIONAL, -- Need M phr-Config   SetupRelease { PHR-Config } OPTIONAL, -- Need M skipUplinkTxDynamic    BOOLEAN,  ...,  [[  csi-Mask-v1530     BOOLEANOPTIONAL, -- Need M  dataInactivityTimer-v1530    SetupRelease {DataInactivityTimer } OPTIONAL  -- Cond MCG-Only  ]] }DataInactivityTimer ::= ENUMERATED {s1, s2, s3, s5, s7, s10, s15, s20,s40, s50, s60, s80, s100, s120, s150, s180}

The proposed timer based configuration: The configuration may beprovided conditional to the present of dataInactivityTimer.

   MAC-CellGroupConfig ::=     SEQUENCE {  drx-Config   SetupRelease {DRX-Config } OPTIONAL, -- Need M  schedulingRequestConfig  SchedulingRequestConfig OPTIONAL, -- Need M  bsr-Config  BSR-ConfigOPTIONAL, -- Need M  tag-Config  TAG-Config OPTIONAL, -- Need M phr-Config   SetupRelease { PHR-Config }  skipUplinkTxDynamic   BOOLEAN,  ...,  [[  csi-Mask-v1530    BOOLEAN OPTIONAL, -- Need M dataInactivityTimer-v1530    SetupRelease { DataInactivityTimer }OPTIONAL,  -- Cond MCG-Only  ]]   [[  inactiveIndicationTimer-r16    SetupRelease { InactiveIndicationTimer }  OPTIONAL -- CondDataInactTimer   ]] } DataInactivityTimer ::= ENUMERATED {s1, s2, s3,s5, s7, s10, s15, s20, s40, s50, s60, s80, s100, s120, s150, s180}InactiveIndicationTimer-r16    ENUMERATED {0dot2, 0dot4, 0dot6, 0dot8}

The MAC-CellGroupConfig field descriptions are provided in table. 1 andthe conditional presence is described in table. 2.

TABLE 1 MAC-CellGroupConfig field descriptions csi-Mask-v1530 If set totrue, the UE limits CSI reports to the on-duration period of the DRXcycle, see TS 38.321 [3]. dataInactivityTimer-v1530 Releases the RRCconnection upon data inactivity as specified in clause 5.3.8.5 and in TS38.321 [3]. Value s1 corresponds to 1 second, s2 corresponds to 2seconds and so on. drx-Config Used to configure DRX as specified in TS38.321 [3]. inactiveIndicationTimer-r16 Triggers UL transmission toindicate the network about need to transition to INACTIVE state due todata inactivity. Value 0dot2 refers to 20% of dataInactivityTimer and soon. skip UplinkTxDynamic If set to true, the UE skips UL transmissionsfor an uplink grant other than a configured uplink grant if no data isavailable for transmission in the UE buffer as described in TS 38.321[3]. FFS: configurable per SCell?

TABLE 2 Conditional Presence Explanation MCG-Only This field isoptionally present, Need M, for the MAC- CellGroupConfig of the MCG. Itis absent otherwise. DataInactTimer The field is optionally present,Need M, for MAC entity when dataInactivityTimer is configured. It isabsent otherwise.

Handling of inactiveIndicationTimer: The MAC may handle this timer basedon data activity on the MAC entity and indicate to RRC once theconfigured threshold timer condition is satisfied.

5.19 Data Inactivity Monitoring (38.321)

The UE may be configured by RRC with a Data inactivity monitoringfunctionality, when in RRC_CONNECTED. RRC controls Data inactivityoperation by configuring the timer dataInactivityTimer.When dataInactivityTimer is configured, the UE shall:1> if inactiveIndicationTimer is not configured;

-   -   2> if any MAC entity receives a MAC SDU for DTCH logical        channel, DCCH logical channel, or CCCH logical channel; or    -   2> if any MAC entity transmits a MAC SDU for DTCH logical        channel, or DCCH logical channel:        -   3> start or restart dataInactivityTimer.    -   2> if the dataInactivityTimer expires:        -   3> indicate the expiry of the dataInactivityTimer to upper            layers.            1> else, if inactiveIndicationTimer is configured;    -   2> if any MAC entity receives a MAC SDU for DTCH logical        channel, DCCH logical channel, or CCCH logical channel; or    -   2> if any MAC entity transmits a MAC SDU for DTCH logical        channel, or DCCH logical channel:        -   3> start or restart inactiveIndicationTimer.    -   2> if the inactiveIndicationTimer expires:        -   3> indicate the expiry of the inactiveIndicationTimer to            upper layers.            5.3.8.6 UE Actions Upon the Expiry of            inactiveIndicationTimer (38.331)            Upon receiving the expiry of inactiveIndicationTimer from            lower layers while in RRC_CONNECTED, the UE shall:            1> initiate transmission of UEAssistanceMessage with            inactiveIndication set.

Alternatively, the network may configure the UE withinactiveIndicationTimer independent of dataInactivityTimer. In suchcases, the handling is as illustrated below:

Configuration: MAC-CellGroupConfig ::=  SEQUENCE {  drx-Config  SetupRelease { DRX-Config } OPTIONAL, -- Need M schedulingRequestConfig   SchedulingRequestConfig OPTIONAL, -- Need M bsr-Config  BSR-Config OPTIONAL, -- Need M  tag-Config  TAG-ConfigOPTIONAL, -- Need M  phr-Config   SetupRelease { PHR-Config } OPTIONAL,-- Need M  skipUplinkTxDynamic    BOOLEAN,  ...,  [[  csi-Mask-v1530   BOOLEAN OPTIONAL, -- Need M  dataInactivityTimer-v1530   SetupRelease { DataInactivityTimer } OPTIONAL -- Cond MCG-Only  ]]  [[  inactiveIndicationTimer-r16     SetupRelease {InactiveIndicationTimer }  OPTIONAL -- Need M   ]] } DataInactivityTimer::= ENUMERATED {s1, s2, s3, s5, s7, s10, s15, s20, s40, s50, s60, s80,s100, s120, s150, s180} InactiveIndicationTimer-r16    ENUMERATED{ms200, ms500, ms1000, ms2000, ms5000, ms10000}

Further, the MAC-CellGroupConfig field descriptions is provided in thetable. 3.

TABLE 3 MAC-CellGroupConfig field descriptions csi-Mask-v1530 If set totrue, the UE limits CSI reports to the on-duration period of the DRXcycle, see TS 38.321 [3]. dataInactivityTimer-v1530 Releases the RRCconnection upon data inactivity as specified in clause 5.3.8.5 and in TS38.321 [3]. Value s1 corresponds to 1 second, s2 corresponds to 2seconds and so on. drx-Config Used to configure DRX as specified in TS38.321 [3]. inactiveIndicationTimer-r16 Triggers UL transmission toindicate the network about need to transition to INACTIVE state due todata inactivity. Value ms 200 refers to 200 ms and so on. skipUplinkTxDynamic If set to true, the UE skips UL transmissions for anuplink grant other than a configured uplink grant if no data isavailable for transmission in the UE buffer as described in TS 38.321[3]. FFS: configurable per SCell?

Handling of inactiveIndicationTimer: The MAC may handle this timer basedon data activity on the MAC entity and indicate to RRC once theconfigured threshold timer condition is satisfied.

5.19 Data Inactivity Monitoring (38.321)

The UE may be configured by RRC with a Data inactivity monitoringfunctionality, when in RRC_CONNECTED. RRC controls Data inactivityoperation by configuring the timer dataInactivityTimer.When dataInactivityTimer is configured, the UE shall:1> if any MAC entity receives a MAC SDU for DTCH logical channel, DCCHlogical channel, or CCCH logical channel; or1> if any MAC entity transmits a MAC SDU for DTCH logical channel, orDCCH logical channel:

-   -   2> start or restart dataInactivityTimer.        1> if the dataInactivityTimer expires:    -   2> indicate the expiry of the dataInactivityTimer to upper        layers.

5.X Inactivity Indication Monitoring (38.321)

When dataInactivityTimer is configured, the UE shall:1> if any MAC entity receives a MAC SDU for DTCH logical channel, DCCHlogical channel, or CCCH logical channel; or1> if any MAC entity transmits a MAC SDU for DTCH logical channel, orDCCH logical channel:

-   -   2> start or restart inactiveIndicationTimer.        1> if the inactiveIndicationTimer expires:    -   2> indicate the expiry of the inactiveIndicationTimer to upper        layers.        5.3.8.6 UE Actions Upon the Expiry of inactiveIndicationTimer        (38.331)        Upon receiving the expiry of inactiveIndicationTimer from lower        layers while in RRC_CONNECTED, the UE shall:        1> initiate transmission of UEAssistanceMessage with        inactiveIndication set.

The proposed counter based configuration: The need for transition toINACTIVE state can be monitored based on a count of DRX cycles withoutdata inactivity. If the configured number of DRX cycles have elapsedwithout any transmission or reception (drxInactivityTimer is not startedeven once during this duration), the UE (100) initiates transmission ofstat transition indication to network.

DRX-Config ::= SEQUENCE {  drx-onDurationTimer CHOICE {  subMilliSecondsINTEGER (1..31),  milliSeconds ENUMERATED {   ms1, ms2, ms3, ms4, ms5,ms6, ms8, ms10, ms20, ms30, ms40, ms50, ms60,   ms80, ms100, ms200,ms300, ms400, ms500, ms600, ms800, ms1000, ms1200,   ms1600, spare8,spare7, spare6, spare5, spare4, spare3, spare2, spare1 }  }, drx-InactivityTimer  ENUMERATED {  ms0, ms1, ms2, ms3, ms4, ms5, ms6,ms8, ms10, ms20, ms30, ms40, ms50, ms60, ms80,  ms100, ms200, ms300,ms500, ms750, ms1280, ms1920, ms2560, spare9, spare8,  spare7, spare6,spare5, spare4, spare3, spare2, spare1},  drx-HARQ-RTT-TimerDL   INTEGER(0..56),  drx-HARQ-RTT-TimerUL   INTEGER (0..56), drx-RetransmissionTimerDL  ENUMERATED {  sl0, sl1, sl2, sl4, sl6, sl8,sl16, sl24, sl33, sl40, sl64, sl80, sl96, sl112, sl128,  sl160, sl320,spare15, spare14, spare13, spare12, spare11, spare10, spare9,  spare8,spare7, spare6, spare5, spare4, spare3, spare2, spare1}, drx-RetransmissionTimerUL  ENUMERATED {  sl0, sl1, sl2, sl4, sl6, sl8,sl16, sl24, sl33, sl40, sl64, sl80, sl96, sl112, sl128,  sl160, sl320,spare15, spare14, spare13, spare12, spare11, spare10, spare9,  spare8,spare7, spare6, spare5, spare4, spare3, spare2, spare1 }, drx-LongCycleStartOffset CHOICE {   ms10  INTEGER(0..9),   ms20 INTEGER(0..19),   ms32  INTEGER(0..31),   ms40  INTEGER(0..39),   ms60 INTEGER(0..59),   ms64  INTEGER(0..63),   ms70  INTEGER(0..69),   ms80 INTEGER(0.. 79),   ms128   INTEGER(0..127),   ms160   INTEGER(0..159),  ms256   INTEGER(0..255),   ms320   INTEGER(0..319),   ms512  INTEGER(0..511),   ms640   INTEGER(0..639),   ms1024  INTEGER(0..1023),   ms1280   INTEGER(0..1279),   ms2048  INTEGER(0..2047),   ms2560   INTEGER(0..2559),   ms5120  INTEGER(0..5119),   ms10240   INTEGER(0..10239)  },  shortDRX SEQUENCE{   drx-ShortCycle  ENUMERATED {   ms2, ms3, ms4, ms5, ms6, ms7, ms8,ms10, ms14, ms16, ms20, ms30, ms32,   ms35, ms40, ms64, ms80, ms128,ms160, ms256, ms320, ms512, ms640, spare9,   spare8, spare7, spare6,spare5, spare4, spare3, spare2, spare1 },   drx-ShortCycleTimer  INTEGER (1..16)  } OPTIONAL, -- Need R  drx-SlotOffset  INTEGER(0..31)   [[   inactiveIndciationCounter-r16  SetupRelease {InactiveIndciationCounter }   ]] } InactiveIndciationCounter ENUMERATED{n2, n5, n10, n25, n100}

Further, the DRX-Config field descriptions is provided in the table. 4.

TABLE 4 DRX-Config field descriptions drx-HARQ-RTT-TimerDL Value innumber of symbols of the BWP where the transport block was received.drx-HARQ-RTT-TimerUL Value in number of symbols of the BWP where thetransport block was transmitted. drx-InactivityTimer Value in multipleintegers of 1 ms. ms 0 corresponds to 0, ms 1 corresponds to 1 ms, ms 2corresponds to 2 ms, and so on. drx-LongCycleStart Offset drx-LongCyclein ms and drx-StartOffset in multiples of 1 ms. If drx- ShortCycle isconfigured, the value of drx-LongCycle shall be a multiple of thedrx-ShortCycle value. drx-onDurationTimer Value in multiples of 1/32 ms(subMilliSeconds) or in ms (milliSecond). For the latter, ms 1corresponds to 1 ms, ms 2 corresponds to 2 ms, and so on.drx-RetransmissionTimerDL Value in number of slot lengths of the BWPwhere the transport block was received. sl0 corresponds to 0 slots, sl1corresponds to 1 slot, sl2 corresponds to 2 slots, and so on.drx-RetransmissionTimerUL Value in number of slot lengths of the BWPwhere the transport block was transmitted. sl0 corresponds to 0 slots,sl1 corresponds to 1 slot, sl2 corresponds to 2 slots, and so on.drx-ShortCycleTimer Value in multiples of drx-ShortCycle. A value of 1corresponds to drx- ShortCycle, a value of 2 corresponds to 2 *drx-ShortCycle and so on. drx-ShortCycle Value in ms. ms 1 correspondsto 1 ms, ms 2 corresponds to 2 ms, and so on. drx-SlotOffset Value in1/32 ms. Value 0 corresponds to 0 ms, value 1 corresponds to 1/32 ms,value 2 corresponds to 2/32 ms, and so on. inactiveIndciationCounterTriggers UL transmission to indicate the network about need totransition to INACTIVE state due to data inactivity. Value n2 refers to2 drx cycles and so on.5.3.8.x UE Actions Upon Satisfying inactiveIndicationCounter (38.331)Upon satisfying the condition of not having and DL reception or ULtransmission for inactiveIndicationCounter count of DRX, from lowerlayers while in RRC_CONNECTED, the UE shall:1> initiate transmission of UEAssistanceMessage with inactiveIndicationset.

Table. 5 illustrates throughput measurements for NR calculated at theRadio link control (RLC) layer based on data volume between referencetime points at the RLC layer. The method to perform Layer 2 throughputmeasurements by gNB/NG-eNB is described. Performance measurements for 5Gnetworks including throughput measurements at gNB are defined in the SA5TS 28.552 “5G performance measurements”. RAN2 also studied thefeasibility of SA5 defined measurements related to RAN2. Generally, thethroughput measurements are calculated at PDCP SDU level based on datavolume between reference time points at PDCP layer in LTE. However, thethroughout measurements for NR are calculated at RLC layer based on datavolume between reference time points at RLC layer as illustrated intable.5.

TABLE 5 LTE: Scheduled IP Throughput NR: Average DL UE throughput in DL(Similar measurement in gNB (Similar measurement defined for as well)defined for as well) The measurement is performed per The measurement isoptionally QCI per UE. split into subcounters per QoS level${{{If}{\sum{ThpTimeDl}}} > 0},{\frac{\sum{ThpVolDl}}{\sum{ThpTimeDl}} \times {1000\mspace{14mu}\left\lbrack {{kbits}\text{/}s} \right\rbrack}}$${{{If}{\sum\limits_{UEs}{\sum{ThpTimeDl}}}} > 0},{\frac{\sum\limits_{UEs}{\sum{ThpVolDl}}}{\sum\limits_{UEs}{\sum{ThpTimeDl}}} \times {1000\mspace{14mu}\left\lbrack {{kbits}\text{/}s} \right\rbrack}}$If ΣThpTimeDl = 0, 0 [kbits/s]${{{If}{\sum\limits_{UEs}{\sum{ThpTimeDl}}}} = 0},{0\mspace{14mu}\left\lbrack {{kbits}\text{/}s} \right\rbrack}$For small data bursts, where all For small data bursts, where allbuffered data is included in one buffered data is included in oneinitial HARQ transmission, initial HARQ transmission, ThpTimeDl = 0,otherwise ThpTimeDl = 0, otherwise ThpTimeDl = T1 − T2 [ms] ThpTimeDl =T1 − T2 [ms] ThpTimeDl The time to transmit a ThpTimeDl The time totransmit a data data burst excluding the burst excluding the data lastpiece of data transmitted in the slot transmitted in the TTI when thebuffer is when the buffer is emptied. A sample of emptied. A sample of″ThpTimeDl″ for each ″ThpTimeDl″ for each time the DL buffer for onetime the DL buffer for DataRadioBearer (DRB) one E-RAB is emptied. isemptied. T1 The point in time after T2 T1 The point in time after T2when data up until the when data up until the second last piece of datasecond last piece of data in in the transmitted data the transmitteddata burst burst which emptied the which emptied the RLC PDCP SDUavailable for SDU available for transmission for the transmission forthe particular E-RAB was particular DRB was successfully transmitted,successfully transmitted, as acknowledged by the as acknowledged by theUE. UE. T2 The point in time when T2 The point in time when the thefirst transmission first transmission begins begins after a PDCP after aRLC SDU becomes SDU becomes available available for transmission, fortransmission, where where previously no RLC previously no PDCP SDUs wereavailable for SDUs were available for transmission for the transmissionfor the particular DRB. particular E-RAB. ThpVolDl The RLC level volumeof ThpVolDl The volume of a data a data burst, excluding the burst,excluding the data data transmitted in the slot transmitted in the TTIwhen the buffer is when the buffer is emptied. A sample for emptied. Asample for ThpVolDl is the data ThpVolDl is the data volume, counted onRLC volume, counted on SDU level, in kbits PDCP SDU level, insuccessfully transmitted kbits successfully (acknowledged by UE) intransmitted DL for one DRB during a (acknowledged by UE) sample ofThpTimeDl. (It in DL for one E-RAB shall exclude the volume during asample of of the last piece of data ThpTimeDl. It shall emptying thebuffer). exclude the volume of the last piece of data emptying thebuffer.

Further, the throughput measurements defined for NR by SA5 may beperformed at RLC layer whereas in LTE, it is measured at PDCP layer.

A QoS flow may be the smallest granularity over which QoS verificationcan be performed by the network. The mapping between QoS flow and DRB inNR is not always one to one and can also be many to one. Therefore,performing throughput measurement at RLC layer alone is not sufficientto verify QoS and identify the throughput per QoS flow. An analysis ofadequacy of RLC level throughput measurements for different possiblebearer configuration on NR is illustrated below:

TABLE 6 Bearer termination point (RAN RLC layer Bearer node withConnected measurement No Type PDCP) CN Sufficient? Remarks 1 Direct gNB5GC NO RB may bearer on have NR multiple QoS flows mapped to it. 2 gNBEPC YES PDCP Throughput = RLC Throughput 3 Split gNB 5GC NO RB may 4bearer on eNB 5GC NO have NR multiple QoS flows mapped to it. 5 gNB EPCYES 6 eNB EPC YES PDCP Throughput = Sum of both RLC entity throughputs

All the bearer types configured on the NR can estimate the QoS correctlyif the throughput measurement is done only based on the RLC data volumeat the RLC layer.

In the NR a PDU session can include multiple QoS flows and SDAP entitycan map one or more QoS flows onto a single DRB. The restriction in theQoS flow to DRB mapping is that one QoS flow is mapped onto only one DRBat a time. For radio bearers on the NR which is connected to 5GC, theQoS termination point on gNB is SDAP entity. Therefore, in order toverify QoS over an IP flow for bearers connected to 5GC, the throughputhas to be measured at SDAP layer. For radio bearer on NR which isconnected to EPC, the QoS termination point on eNB is PDCP entity. Inorder to verify QoS for an IP flow for bearers connected to EPC, thethroughput has to be measured at PDCP entity. The method proposes thatfor the NR and the LTE bearers connected to 5GC, the throughputmeasurement has to be done based on the SDAP SDU at the SDAP layer. Themethod proposes that for the NR and the LTE bearers connected to EPC,the throughput measurement has to be done based on the PDCP SDU at thePDCP layer.

In case of split bearers, the PDCP throughput may not always bereflected as the sum of throughputs of the RLC entities it is connectedto. For radio bearers for which PDCP duplication is configured, thethroughput measurement has to be performed based on PDCP SDU volume. Themethod proposes that for the radio bearers configured with the PDCPduplication, the throughput measurement has to be done based on the PDCPSDU at the PDCP layer.

In MR-DC cases, there are split bearers that can be configured withtermination point on gNB/NR and the split leg on eNB/LTE. In such cases,in order to measure throughput over the DRB, the gNB has to consider thethroughput provided over both the legs. Therefore, the gNB would add thethroughput on NR RLC entity and LTE RLC entity. However, there is nothroughput measurement performed on LTE RLC as per current release 15specification. Provision to measure throughput based on RLC SDU on LTE,for split bearers terminating on gNB, has to be introduced. It isproposed that introduce throughput measurement based on RLC SDU at RLClayer on eNB, when split bearer with termination on gNB is configured tothe UE (100).

FIG. 8 illustrates a gNB according to the embodiments as disclosedherein.

The gNBs, eNBs or BSs described above may correspond to the gNB 800. Forexample, the source gNB (1000 a) and/or the target gNB (1000 b)illustrated in FIG. 1A may correspond to the gNB 800.

Referring to the FIG. 8, the gNB 800 may include a processor 830, atransceiver 810 and a memory 820. However, all of the illustratedcomponents are not essential. The gNB 800 may be implemented by more orless components than those illustrated in FIG. 8. In addition, theprocessor 830 and the transceiver 810 and the memory 820 may beimplemented as a single chip according to another embodiment.

The aforementioned components will now be described in detail.

The processor 830 may include one or more processors or other processingdevices that control the proposed function, process, and/or method.Operation of the gNB 800 may be implemented by the processor 830.

The processor 830 may control the transceiver 810 to transmit a radioresource control (RRC) reconfiguration message to UE when the UE is inan RRC connected state. The RRC reconfiguration message may include ahandover configuration.

The transceiver 810 may include a RF transmitter for up-converting andamplifying a transmitted signal, and a RF receiver for down-converting afrequency of a received signal. However, according to anotherembodiment, the transceiver 810 may be implemented by more or lesscomponents than those illustrated in components.

The transceiver 810 may be connected to the processor 830 and transmitand/or receive a signal. The signal may include control information anddata. In addition, the transceiver 810 may receive the signal through awireless channel and output the signal to the processor 830. Thetransceiver 810 may transmit a signal output from the processor 830through the wireless channel.

The memory 820 may store the control information or the data included ina signal obtained by the gNB 800. The memory 820 may be connected to theprocessor 830 and store at least one instruction or a protocol or aparameter for the proposed function, process, and/or method. The memory830 may include read-only memory (ROM) and/or random access memory (RAM)and/or hard disk and/or CD-ROM and/or DVD and/or other storage devices.

FIG. 9 illustrates a user equipment (UE) according to the embodiments asdisclosed herein.

The UEs described above may correspond to the UE 900. For example, theUE 100 illustrated in FIG. 1A and FIG. 1B may correspond to the UE 900.

Referring to the FIG. 9, the UE 900 may include a processor 930, atransceiver 910 and a memory 920. However, all of the illustratedcomponents are not essential. The UE 900 may be implemented by more orless components than those illustrated in FIG. 9. In addition, theprocessor 930 and the transceiver 910 and the memory 920 may beimplemented as a single chip according to another embodiment.

The aforementioned components will now be described in detail.

The processor 930 may include one or more processors or other processingdevices that control the proposed function, process, and/or method.Operation of the UE 900 may be implemented by the processor 930.

The processor 930 may control the transceiver 910 to receive a radioresource control (RRC) reconfiguration message from a source cell of thewireless communication network, wherein the UE is in an RRC connectedstate and wherein the RRC reconfiguration message comprises a handoverconfiguration. In addition, the processor 930 may determine whether aCHO configuration is provided in the handover configuration, wherein theCHO configuration comprises a plurality of conditions for executing theCHO and a plurality of target cell configurations. The processor 930 mayperform one of: continuing a Radio Link Monitoring (RLM) timer and aradio link monitoring procedure on the source cell, in response todetermining that the CHO configuration is provided in the handoverconfiguration, and stopping the RLM timer and suspending the radio linkmonitoring procedure on the source cell, in response to determining thatthe CHO configuration is not provided in the handover configuration. Theprocessor 930 may execute the CHO from the source cell to a candidatetarget cell of the plurality of target cells in the wirelesscommunication network based on the CHO configuration.

The transceiver 910 may include a RF transmitter for up-converting andamplifying a transmitted signal, and a RF receiver for down-converting afrequency of a received signal. However, according to anotherembodiment, the transceiver 910 may be implemented by more or lesscomponents than those illustrated in components.

The transceiver 910 may be connected to the processor 930 and transmitand/or receive a signal. The signal may include control information anddata. In addition, the transceiver 910 may receive the signal through awireless channel and output the signal to the processor 930. Thetransceiver 910 may transmit a signal output from the processor 930through the wireless channel.

The memory 920 may store the control information or the data included ina signal obtained by the UE 900. The memory 920 may be connected to theprocessor 920 and store at least one instruction or a protocol or aparameter for the proposed function, process, and/or method. The memory3330 may include read-only memory (ROM) and/or random access memory(RAM) and/or hard disk and/or CD-ROM and/or DVD and/or other storagedevices.

The embodiments disclosed herein can be implemented through at least onesoftware program running on at least one hardware device and performingnetwork management functions to control the elements.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the embodiments herein that others can, byapplying current knowledge, readily modify and or adapt for variousapplications such specific embodiments without departing from thegeneric concept, and, therefore, such adaptations and modificationsshould and are intended to be comprehended within the meaning and rangeof equivalents of the disclosed embodiments. It is to be understood thatthe phraseology or terminology employed herein is for the purpose ofdescription and not of limitation. Therefore, while the embodimentsherein have been described in terms of preferred embodiments, thoseskilled in the art will recognize that the embodiments herein can bepracticed with modification within the spirit and scope of theembodiments as described herein.

Although the present disclosure has been described with variousembodiments, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A method performed by a terminal in a wirelesscommunication network, comprising: receiving, from a base station, aRadio Resource control (RRC) reconfiguration message includinginformation indicating that the terminal is allowed to transmitpreferred state information to leave a connected state; identifyingwhether the terminal prefers to transition out of a connected state; andin case that the terminal prefers to transition out of the connectedstate, transmitting, to the base station, assistance informationincluding the preferred state information, wherein the preferred stateinformation includes information indicating an idle state, informationindicating an inactive state, or information indicating out of theconnected state.
 2. The method of claim 1, wherein the identifyingwhether the terminal prefers to transition out of the connected statecomprises: identifying a timer associated with the preferred stateinformation is not running.
 3. The method of claim 2, furthercomprising: starting the timer associated with the preferred stateinformation when the assistance information including the preferredstate information is transmitted.
 4. The method of claim 1, furthercomprising: receiving, from the base station, an RRC release message fortransition out of the connected state based on the assistanceinformation including the preferred state information; and entering anidle state or an inactive state based on the RRC release message.
 5. Themethod of claim 1, wherein the RRC reconfiguration message includesconditional handover (CHO) configuration information; and wherein themethod further comprises: identifying one or more execution conditionsfor performing CHO and a plurality of target cell configurationsincluded in first CHO configuration information; continuing a Radio LinkMonitoring (RLM) timer and an RLM procedure on a source cell until afirst candidate target cell from a plurality of candidate target cellssatisfies at least one execution condition from the one or moreexecution conditions for performing the CHO; and in case that the firstcandidate target cell satisfies the at least one execution conditionfrom the one or more execution conditions for performing the CHO,executing the CHO.
 6. A method performed by a base station (BS) in awireless communication network, comprising: transmitting, to a terminal,a Radio Resource control (RRC) reconfiguration message includinginformation indicating the terminal is allowed to transmit preferredstate information to leave a connected state; and in case that theterminal prefers to transition out of the connected state, receiving,from the terminal, assistance information including the preferred stateinformation, wherein the preferred state information includesinformation indicating an idle state, information indicating an inactivestate, or information indicating out of the connected state.
 7. Themethod of claim 6, wherein a timer associated with the preferred stateinformation is not running when the terminal prefers to transition outof the connected state.
 8. The method of claim 7, wherein the timerassociated with the preferred state information is started when theassistance information including the preferred state information istransmitted.
 9. The method of claim 6, further comprising: transmitting,to the terminal, an RRC release message including information fortransition out of the connected state of the terminal based on theassistance information including the preferred state information,wherein the terminal enters an idle state or an inactive state based onthe RRC release message.
 10. The method of claim 6, wherein the RRCreconfiguration message includes conditional handover (CHO)configuration information; and wherein the method further comprises:identifying that a Radio Link Monitoring (RLM) procedure on a sourcecell is continued until a first candidate target cell from a pluralityof candidate target cells satisfies at least one execution conditionfrom the one or more execution conditions for performing the CHO; andidentifying that the RLM procedure on the source cell is suspended whenthe first candidate target cell satisfies at least one executioncondition from the one or more execution conditions for performing theCHO.
 11. A terminal in a wireless communication network, the terminalcomprising: a transceiver; and at least one processor coupled to thetransceiver, the at least one processor configured to: control thetransceiver to receive, from a base station, a Radio Resource control(RRC) reconfiguration message including information indicating theterminal is allowed to transmit preferred state information to leave aconnected state, identify whether the terminal prefers to transition outof a connected state, and control the transceiver to transmit, to thebase station, assistance information including the preferred stateinformation in case that the terminal prefers to transition out of theconnected state, wherein the preferred state information includesinformation indicating an idle state, information indicating an inactivestate, or information indicating out of the connected state.
 12. Theterminal of claim 11, wherein the at least one processor is furtherconfigured to: identify a timer associated with the preferred stateinformation is not running.
 13. The terminal of claim 12, wherein the atleast one processor is further configured to: start the timer associatedwith the preferred state information when the assistance informationincluding the preferred state information is transmitted
 14. Theterminal as claimed in claim 11, wherein the at least one processor isfurther configured to: control the transceiver to receive, from the basestation, an RRC release message for transition out of the connectedstate based on the assistance information including the preferred stateinformation, and enter an idle state or an inactive state based on theRRC release message.
 15. The terminal as claimed in claim 11, whereinthe RRC reconfiguration message includes conditional handover (CHO)configuration information; and wherein the at least one processor isfurther configured to: identify one or more execution conditions forperforming CHO and a plurality of target cell configurations included infirst CHO configuration information, continue a Radio Link Monitoring(RLM) timer and an RLM procedure on a source cell until a firstcandidate target cell from a plurality of candidate target cellssatisfies at least one execution condition from the one or moreexecution conditions for performing the CHO, and in case that the firstcandidate target cell satisfies the at least one execution conditionfrom the one or more execution conditions for performing the CHO,execute the CHO.
 16. A base station (BS) in a wireless communicationnetwork, comprising: a transceiver; and at least one processor coupledto the transceiver, the at least one processor configured to: controlthe transceiver to transmit, to a terminal, a Radio Resource control(RRC) reconfiguration message including information indicating theterminal is allowed to transmit preferred state information to leave aconnected state, and control the transceiver to receive, from theterminal, assistance information including the preferred stateinformation in case that the terminal prefers to transition out of theconnected state, wherein the preferred state information includesinformation indicating an idle state, information indicating an inactivestate, or information indicating out of the connected state.
 17. The BSof claim 16, wherein a timer associated with the preferred stateinformation is not running when the terminal prefers to transition outof the connected state.
 18. The BS of claim 17, wherein the timerassociated with the preferred state information is started when theassistance information including the preferred state information istransmitted.
 19. The BS of claim 16, wherein the at least one processoris further configured to: control the transceiver to transmit, to theterminal, an RRC release message including information for transitionout of the connected state of the terminal based on the assistanceinformation including the preferred state information, wherein theterminal enters an idle state or an inactive state based on the RRCrelease message.
 20. The BS of claim 16, wherein the RRC reconfigurationmessage includes conditional handover (CHO) configuration information;and wherein the at least one processor is further configured to:identify that a Radio Link Monitoring (RLM) procedure on a source cellis continued until a first candidate target cell from a plurality ofcandidate target cells satisfies at least one execution condition fromthe one or more execution conditions for performing the CHO, andidentify that the RLM procedure on the source cell is suspended when thefirst candidate target cell satisfies at least one execution conditionfrom the one or more execution conditions for performing the CHO.